The primary focus of this project and the hypothesis for which the sample size calculations were designed around is whether or not minimally invasive trans-luminal mediastinal LN biopsy is as accurate as traditional "gold standard" techniques in the diagnosis and staging of the mediastinum. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy will be calculated for both strategies (minimally invasive and traditional) and compared. Receiver operating curves will be used to compare the two strategies at differing sensitivity and 1-specificity values. Relative operating characteristic curves will be used to compare the two strategies at different true positive and false positive rates. The study is estimated to be completed in three years. Sample size calculation has determined that 166 patients are required for the study. The thoracic surgery division at the CHUM estimates that accrual will be approximately 1.5 patients per week (6 patients/month).